milk

[fatlil]

Does milk go sour in a thunderstorm if left out of the fridge and if it does why?

[gen2]

The short answer is no.

This Old Wives Tale originates before the invention of fridges. Milk bottles would be stood in a porous clay container and stood in a little water. The water soaked through the clay and evaporated and as you may remember from your science classes, 'Evaporation Produces Cooling'. This kept the milk cool and fresh for longer.

Now Thundertorms occur when the air is humid and hot. If the air is humid, then evaporation (and hence the cooling) will not happen. The hot air will cause the milk to warm up and sour faster since the souring is caused by bacteria present in the milk and they grow faster when it is warm.

The thunderstorm itself is not the cause of the souring, it is heat and bacteria.

Finally one should note that modern processing of milk (micro-filtration) means that there are fewer bacteria present to start with than there used to be in the past. Moden milk will sour more slowly than great-granny's milk.

[fatlil]

What a brilliant answer. Thanks very much.